In 3GPP (3rd Generation Partnership Project), a W-CDMA scheme has been standardized as a third-generation cellular mobile communication scheme, and services based on the scheme have been sequentially started. Also, HSDPA with higher communication speed has been standardized, and services based thereon have been started.
Meanwhile, in 3GPP, standardization of evolved third-generation radio access (Evolved Universal Terrestrial Radio Access, hereinafter referred to as “EUTRA”) is progressing. As a downlink communication scheme of EUTRA, an OFDM (Orthogonal Frequency Division Multiplexing) scheme, which is resistant to multipath interference and is suitable for high-speed transmission, has been employed. As an uplink communication scheme, a DFT (Discrete Fourier Transform)-spread OFDM scheme of an SC-FDMA (Single Carrier-Frequency Division Multiple Access) scheme, in which peak to average power ratio (PAPR) of a transmit signal can be reduced, has been employed in consideration of the cost and power consumption of mobile station apparatuses.
Furthermore, in 3GPP, discussions over Advanced-EUTRA, which is further advancement of EUTRA, have started. Advanced-EUTRA assumes communications that is performed at a transmission rate of up to 1 Gbps or more in downlink and up to 500 Mbps or more in uplink by using a band having a bandwidth of up to 100 MHz in each of the uplink and the downlink.
In Advanced-EUTRA, it is considered that a band of up to 100 MHz is to be realized by aggregating a plurality of bands of EUTRA, each having a bandwidth of 20 MHz or less, so that mobile station apparatuses of EUTRA can be supported. In Advanced-EUTRA, each band of EUTRA of 20 MHz or less is called a “component carrier (CC)” (see NPL 2). One downlink component carrier and one uplink component carrier form one cell. One downlink component carrier alone can form one cell. A base station apparatus assigns a plurality of cells to a mobile station apparatus, and communicates with the mobile station apparatus via the assigned cells.
Also, in Advanced-EUTRA, it is studied that a base station apparatus and a mobile station apparatus communicate with each other via a plurality of component carriers via a repeater or an RRH (Radio Remote Head), as illustrated in FIG. 12. In such a case, reception timing at which the mobile station apparatus receives data from a downlink component carrier may vary among individual cells. Also, transmission timing (Timing Advance: TA) at which the mobile station apparatus transmits data to the base station apparatus may vary among uplink component carriers of individual cells. Thus, the mobile station apparatus adjusts transmission timing for the uplink component carrier of each cell or for each group of component carriers having an identical transmission timing. A group of component carriers (or cells) having an identical transmission timing is referred to as a “transmission timing group (TA group)”.
The base station apparatus sets a transmission timing group to a mobile station apparatus to which cells of different transmission timings have been assigned. Also, the base station apparatus resets a transmission timing group to the mobile station apparatus in accordance with a change in communication status.